Sebastian Junger, the author of the best-selling book, "The Perfect Storm," lived for months with American troops as they meandered through some incredibly violent corners of Afghanistan. In his new book, "War," Junger tells the story of a horrendously intense journey these brave soldiers take through enemy gunfire, including Medal of Honor recipient Staff Sgt. Salvatore Giunta.

Read an excerpt of the book below.

Chapter 2: Killing

The soldiers walk single file along the crest of the spur spaced ten or fifteen yards apart. The terrain falls off steeply on both sides into holly forests and shale scree. The moon is so bright that they're not even using night vision gear.

Unknown to Winn and his men, three enemy fighters are arrayed across the crest of the ridge below them, waiting with AK-47s.

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Nightline Flashback: An American Hero

Parallel to the trail are ten more fighters with belt-fed machine guns and RPGs. In the U.S. military, this is known as an "L-shaped ambush." Correctly done, a handful of men can wipe out an entire platoon. Walking point is Sergeant Josh Brennan, an alpha team leader. He's followed by a SAW gunner named Eckrode and then Staff Sergeant Erick Gallardo and then Specialist Sal Giunta, bravo team leader. Giunta is from Iowa and joined the Army after hearing a radio commercial while working at a Subway sandwich shop in his hometown.

"Out of nothing -- out of taking your next step -- just rows of tracers, RPGs, everything happening out of nowhere with no real idea of how it just fucking happened -- but it happened," Giunta told me.

"Everything kind of slowed down and I did everything I thought I could do, nothing more and nothing less."

The Apache pilots watch this unfold below them but are powerless to help because the combatants are too close together. At the bottom of the hill, Second Platoon hears an enormous fi refi ght erupt, but they too just hold their fire and hope it turns out well. At fi rst, the sheer volume of firepower directed at Brennan's squad negates any conceivable tactical response.

A dozen Taliban fighters with rockets and belt-fed machine guns are shooting from behind cover at a distance of fi fteen or twenty feet; First Platoon is essentially inside a shooting gallery. Within seconds, every man in the lead squad takes a bullet. Brennan goes down immediately, wounded in eight places.

Eckrode takes rounds through his thigh and calf and falls back to lay down suppressive fi re with his SAW. Gallardo takes a round in his helmet and falls down but gets back up. Doc Mendoza, farther down the line, takes a round through the femur and immediately starts bleeding out.

After months of fighting an enemy that stayed hundreds of yards away, the shock of facing them at a distance of twenty feet cannot be overstated. Giunta gets hit in his front plate and in his assault pack and he barely notices except that the rounds came from a strange direction.

Sheets of tracers are coming from his left, but the rounds that hit him seemed to come from dead ahead. He's down in a small washout along the trail where the lip of packed earth should have protected him, but it didn't. "That's when I kind of noticed something was wrong," Giunta said.

"The rounds came right down the draw and there are three people -- all friends -- in the same vicinity. It happened so fast, you don't think too hard about it, but it's something to keep in mind."

Much later, a military investigation will determine that the enemy was trying to throw up a "wall of lead" between the fi rst few men and the rest of the unit so that they could be overrun and captured. Gallardo understands this instinctively and tries to push through the gunfire to link up with his alpha team, Brennan and Eckrode.

Twenty or thirty RPGs come sailing into their position and explode among the trees. When Gallardo goes down with a bullet to the helmet, Giunta runs over to him to drag him behind cover, but Gallardo gets back on his feet immediately. They're quickly joined by Giunta's SAW gunner, PFC Casey, and the three men start pushing forward by throwing hand grenades and sprinting between the blasts.

Even enemy who are not hit are so disoriented by the concussion that they have trouble functioning for a second or two. The group quickly makes it to Eckrode, who's wounded and desperately trying to fix an ammo jam in his SAW, and Gallardo and Casey stay with him while Giunta continues on his own.

He throws his last grenade and then sprints the remaining ground to where Brennan should be. The Gatigal spur is awash in moonlight, and in the silvery shadows of the holly forests he sees two enemy fighters dragging Josh Brennan down the hillside. He empties his M4 magazine at them and starts running toward his friend.

The Army has a certain interest in understanding what was going through Giunta's mind during all of this, because whatever was going through his mind helped save the entire unit from getting killed. A year or so later, several squads of American soldiers conducted an identical L-shaped ambush at night on the Abas Ghar and wiped out a column of Taliban fighters -- nearly twenty men.

The reason First Platoon did not get wiped out had nothing to do with the Apaches fl ying overhead or the 155s at Blessing; it was because the men reacted not as individuals but as a unit. Stripped to its essence, combat is a series of quick decisions and rather precise actions carried out in concert with ten or twelve other men.

In that sense it's much more like football than, say, like a gang fi ght. The unit that choreographs their actions best usually wins. They might take casualties, but they win.

That choreography -- you lay down fi re while I run forward, then I cover you while you move your team up -- is so powerful that it can overcome enormous tactical deficits.

There is choreography for storming Omaha Beach, for taking out a pillbox bunker, and for surviving an L-shaped ambush at night on the Gatigal. The choreography always requires that each man make decisions based not on what's best for him , but on what's best for the group. If everyone does that, most of the group survives. If no one does, most of the group dies.

That, in essence, is combat.

Most firefights go by so fast that acts of bravery or cowardice are more or less spontaneous. Soldiers might live the rest of their lives regretting a decision that they don't even remember making; they might receive a medal for doing something that was over before they even knew they were doing it. When Congressional Medal of Honor recipient Audie Murphy was asked why he took on an entire company of German infantry by himself, he replied famously, "They were killing my friends."

Wars are won or lost because of the aggregate effect of thousands of decisions like that during fi refi ghts that often last only minutes or seconds. Giunta estimates that not more than ten or fifteen seconds elapsed between the initial attack and his own counterattack.

An untrained civilian would have experienced those ten or fifteen seconds as a disorienting barrage of light and noise and probably have spent most of it curled up on the ground. An entire platoon of men who react that way would undoubtedly die to the last man.

Giunta, on the other hand, used those fi fteen seconds to assign rates and sectors of fi re to his team, run to Gallardo's assistance, assess the direction of a round that hit him in the chest, and then throw three hand grenades while assaulting an enemy position.

Every man in the platoon -- even the ones who were wounded -- acted as purposefully and efficiently as Giunta did. For obvious reasons, the Army has tried very hard to understand why some men respond effectively in combat and others just freeze.

"I did what I did because that's what I was trained to do," Giunta told me. "There was a task that had to be done, and the part that I was gonna do was to link alpha and bravo teams. I didn't run through fire to save a buddy -- I ran through fire to see what was going on with him and maybe we could hide behind the same rock and shoot together. I didn't run through fi re to do anything heroic or brave. I did what I believe anyone would have done."

During World War II, the British and American militaries conducted a series of studies to identify what makes men capable of overcoming their fears. A psychiatrist named Herbert Spiegel, who accompanied American troops on the Tunisia campaign, called it the "X-factor": "Whether this factor was conscious or unconscious is debatable," he wrote for a military journal in 1944, "but this is not so important. The important thing was that it is infl uenced greatly by devotion to their group or unit, by regard for their leader and by conviction for their cause. In the average soldier, which most of them were, this factor ... enabled men to control their fear and combat their fatigue to a degree that they themselves did not believe possible."

The U.S. military found that, to a great degree, fearfulness was something they couldn't do much about. A fearful man is likely to remain that way no matter what kind of training he undergoes. During one experiment, completely untrained airborne candidates were told to jump off a thirty four-foot tower. They jumped in a harness that allowed them to fall about twelve feet and then ride a 400-foot cable to the ground. As easy as it sounds, more than half of a group of qualifi ed paratroopers said that jumping off the tower was more frightening than jumping out of a real airplane.

The military tested roughly thirteen hundred candidates on the tower and then tracked their success through airborne school. They found that the men who were "slow" to jump off the tower were more than twice as likely to fail out of the program as "fast" jumpers, and those who refused to jump at all were almost guaranteed to fail.

One of the most puzzling things about fear is that it is only loosely related to the level of danger. During World War II, several airborne units that experienced some of the fiercest fighting of the war also reported some of the lowest psychiatric casualty rates in the U.S. military. Combat units typically suffer one psychiatric casualty for every physical one, and during Israel's Yom Kippur War of 1973, frontline casualty rates were roughly consistent with that
ratio. But Israeli logistics units, which were subject to far less danger, suffered three psychiatric cases for every physical one. And even frontline troops showed enormous variation in their rate of psychological breakdown. Because many Israeli offi cers literally led from the front, they were four times more likely to be killed or wounded than their men were -- and yet they suffered one-fi fth the rate of psychological collapse. The primary factor determining breakdown in combat does not appear to be the objective level of danger so much as the feeling -- even the illusion -- of control. Highly trained men in extraordinarily dangerous circumstances are less likely to break down than untrained men in little danger.

The division between those who feel in control of their fate and those who don't can occur even within the same close-knit group. During World War II, British and American bomber crews experienced casualty rates as high as 70 percent over the course of their tour; they effectively flew missions until they were killed. On those planes, pilots reported experiencing less fear than their turret gunners, who were crucial to operations but had no direct control over the aircraft. Fighter pilots, who suffered casualty rates almost as high as bomber crews, nevertheless reported extremely low levels of fear. They were both highly trained and entirely in control of their own fate, and that allowed them to ignore the statistical reality that they had only a fifty-fifty chance of surviving their tour.

Among men who are dependent on one another for their safety -- all combat soldiers, essentially -- there is often an unspoken agreement to stick together no matter what. The reassurance that you will never be abandoned seems to help men act in ways that serve the whole unit rather than just themselves. Sometimes, however, it effectively amounts to a suicide pact. During the air war of 1944, a four-man combat crew on a B-17 bomber took a vow to never abandon one another no matter how desperate the situation.
(A fifth team member, the top turret gunner, was not part of the
pact.)

The aircraft was hit by fl ak during a mission and went into a terminal dive, and the pilot ordered everyone to bail out. The top turret gunner obeyed the order, but the ball turret gunner discovered that a piece of flak had jammed his turret and he could not get out. The other three men in his pact could have bailed out with parachutes, but they stayed with him until the plane hit the ground and exploded.

They all died.

One of the Taliban fi ghters falls to the ground, dead, and the other releases Brennan and escapes downhill through the trees. Giunta jams a new magazine into his gun and yells for a medic. Brennan is lying badly wounded in the open and Giunta grabs him by the vest and drags him behind a little bit of cover.

He cuts the ammo rack off his chest and pulls the rip cord on his ballistic vest to extricate him from that and then cuts his clothing off to look for wounds. Brennan's been hit multiple times in the legs and has a huge shrapnel wound in his side and has been shot in the lower half of his face. He's still conscious and keeps complaining that there's something in his mouth. It's his teeth, though Giunta doesn't tell him that.

The B-1 fl ying overhead drops two bombs on Hill 1705, and that stuns the enemy enough that the Americans are able to consolidate their position. The Third Platoon medic arrives and gives Brennan a tracheotomy so he can breathe better, and then they get him ready for the MEDEVAC. A Spectre gunship and a couple of Apaches are finally able to distinguish Americans from the enemy and start lighting up the hillsides with cannon and gunfi re, and half an hour later the MEDEVAC comes in and they start hoisting casualties off the ridge.

When they're done, the rest of First Platoon shoulder their gear and resume walking home. "We waited for First Platoon for hours," Hijar told me about that night, "and once we linked up with them it was still two and a half hours' walk back to the KOP. You could just tell on the guys' faces, it wasn't the right time to ask. You already knew what the answer was going to be. Some of them were walking around with bullet holes in their helmets."

Brennan doesn't survive surgery. Mendoza is dead before he even leaves the ridge. Five more men are wounded.

Then there's Rougle from the day before, as well as Rice and
Vandenberge. It's been a costly week. It's been the kind of
week that makes people back home think that maybe we're
losing the war.

From the book WAR (c) 2010 by Sebastian Junger. Reprinted by permission of Twelve Books/Hachette Book Group, New York, NY. All rights reserved.